Presently available imaging diagnostic apparatuses for capturing diagnostic images of patients include CT scanners, MRI (Magnetic Resonance Imaging) apparatuses, PET (Positron Emission Tomography) apparatuses, ultrasonic diagnostic apparatuses, CT angiography apparatuses, MRA (MR angiography) apparatuses and the like. When the abovementioned imaging diagnostic apparatuses are used, a liquid such as a contrast medium and physiological saline may be injected into a patient. Chemical liquid injectors for automatically performing the injection have been put into practical use.
Such a chemical liquid injector has a piston driving mechanism formed of a driving motor, a slider mechanism and the like, for example. A liquid syringe is removably mounted on the chemical liquid injector. The liquid syringe typically comprises a cylinder member and a piston member slidably inserted in the cylinder member.
More particularly, the cylinder member is formed in a cylindrical shape having a closed leading end and an opened trailing end. The cylinder member has a conduit formed at the center of the leading end and an annular cylinder flange formed on the outer circumference of the trailing end. The piston member is slidably inserted into the interior of cylinder member from the trailing end.
There are a pre-filled type and a type filled with nothing in the liquid syringe. The liquid syringe of the pre-filled type includes a cylinder member filled with a liquid and is wholly sealed by a packing material for shipment. In the liquid syringe of the type filled with nothing, a cylinder member is filled with a desired liquid by a user. For simplicity, the following description will be made assuming that the liquid syringe of the pre-filled type is used.
For injecting the liquid into a patient from the liquid syringe of the abovementioned type, an operator prepares for a liquid syringe containing an appropriate liquid and takes out the liquid syringe from the packing material. The operator connects the liquid syringe to the patient through an extension tube and mounts the liquid syringe on the chemical liquid injector. The mounting on the chemical liquid injector is performed by causing a flange holding mechanism of the chemical liquid injector to hold the cylinder flange. In this state, the chemical liquid injector operates the piston driving mechanism in response to a predetermined operation by the operator. This presses the piston member into the cylinder member to inject the liquid into the patient from the liquid syringe.
The operator determines the rate at which the liquid is injected and the total quantity of the liquid to be injected in view of the type of the liquid and the like, and enters data representing the rate and total quantity into the chemical liquid injector. The chemical liquid injector injects the liquid into the patient based on the entered data. For example, if a contrast medium is injected as the liquid, the image contrast of the patient is changed to allow the imaging diagnostic apparatus to capture a favorable diagnostic image of the patient.
Some chemical liquid injectors can inject physiological saline as well as the contrast medium into the patient. In such a chemical liquid injector, the operator enters as desired an instruction to inject the physiological saline following the completion of the injection of the contrast medium, together with data representing the injection rate and total quantity of the physiological saline, into the chemical liquid injector. The chemical liquid injector first injects the contrast medium into the patient based on the entered data and then automatically injects the physiological saline. Consequently, the subsequently injected physiological saline can push the contrast medium to reduce the consumption of the contrast medium and also can reduce artifacts in the captured image.
The contrast medium has a high viscosity. Since the chemical liquid injector can press the piston member into the cylinder member at high pressure, the injector is preferably used for injection of the contrast medium. To insert the piston member into the cylinder member at high pressure, however, the cylinder member needs to be held securely.
Thus, a chemical liquid injector invented and conducted by the applicant of the present application includes a pair of metallic flange holding members supported openably or closably. The paired flange holding members hold individually the left and the right of a cylinder flange of a liquid syringe put on a chemical liquid injector (see, for example, Japanese Patent Laid-Open No. 2004-187849).
In the chemical liquid injector as described above, the pair of metallic flange holding members can securely hold the cylinder flange of the liquid syringe. In consequence, the piston member can be inserted into the cylinder member at high pressure to satisfactorily inject the contrast medium with high viscosity and the like into a patient.
In typical liquid syringes currently used, the cylinder flange has a pair of flat portions in parallel at opposite positions on the circular outer circumference in order to prevent unnecessary rolling and the like of the liquid syringe. The conventional chemical liquid injector is formed to hold the circular portion of the cylinder flange with the flange holding members, and the operator needs to ensure the holding of the circular portion of the cylinder flange with the flange holding members without fail.
If the flange holding members hold the flat portions of the cylinder flange, however, the operator may see it as if the liquid syringe was appropriately held in the chemical liquid injector. In this case, since a smaller area of the cylinder flange is held by the flange holding members, the cylinder flange may be broken easily.
In addition, for injecting the liquid from the liquid syringe into the patient in the abovementioned chemical liquid injector, the operator needs to select the appropriate liquid syringe in order to inject the appropriate liquid. However, since some liquid syringes have the same or similar appearances even when they contain different types of liquid, this leads to the possibility that the operator may mount the liquid syringe containing an inappropriate liquid on the chemical liquid injector.
In some cases, an improper product for a chemical liquid injector may be used as a liquid syringe. In this case, the inappropriate performance thereof such as low resistance to pressure may cause medical malpractice. The liquid syringe of the pre-filled type should be discarded after it is used once in order to prevent infection and the like. As for the currently available chemical liquid injectors, however, it is impossible to prevent reuse of a liquid syringe reliably after it is used once.
As described above, the operator needs to enter data representing the injection rate and total quantity of the liquid and the like for each of the liquid and the liquid syringe into the chemical liquid injector. Since the entry operation is complicated and difficult for an unskilled operator, entry of incorrect numerical values cannot be avoided. The currently available contrast media contain active ingredients which differ in concentration severalfold at maximum. If correct numerical values are not entered, the patient may be injected with the contrast medium of the quantity which is several times larger than or a fraction of the appropriate quantity.
The operator needs to enter data representing the injection rate or the like of the liquid into the chemical liquid injector in some cases based on the area to be imaged and the weight of the patient. The entry operation is also complicated and erroneous entry cannot be prevented. The present applicant has applied that a contrast medium is injected at a variable rate to improve the resulting image contrast (Japanese Patent Laid-Open No. 2004-113475). However, it is not easy to enter the data representing such a variable pattern into the chemical liquid injector.